简单分段故障程序

Question

    PNG * original;
    original->readFromFile("in.png");
    int width  = original->width(); 
    int height = original->height();

I'm getting a segmentation fault in this bit of code. What am I doing wrong?

Answer 1

You must allocate memory, because original it's just a pointer.

Like this:

PNG *original = new PNG();

Answer 2

You are dereferencing original without first having assigned anything to it.

You declared it as a PNG * but did not assign an object instance to that pointer.

Answer 3

Perhaps you don't need to use a pointer

PNG original;
original.readFromFile("in.png");
int width  = original.width(); 
int height = original.height();

Despite what some newbies seem to think pointers are not obligatory.